Enhanced polymer concrete composition

ABSTRACT

A polymer concrete pipe liner is formed from a fluidized, but substantially waterless cement containing mixture applied to the pipe interior. The mixture is composed of inorganic cement particles, a liquid styrene mixture and a minor amount of one or more poly-olefinically unsaturated co-monomers. The mixture substantially excludes acrylonitrile and acrylamide. The co-monomers are preferable selected from a group including trimethylolpropane-trimethacrylate, divinyl benzene, hexadiene, and polyvinylsiloxanes. Mixing the liquid and solid components forms a slurry which is transferred to a pipe interior. Transfer properties can be controlled by particulate gradation, dissolved polymers, and rheology control additives. The pipe is then spun to centrifugally cast the liner. The composition avoids the need for high temperature curing and toxic reactive unsaturates to co-polymerize and cross-link polystyrene. Like the current polymer concrete materials, the materials embodied in the present invention have adequate strength at geothermal operating temperatures and reduced permeability, but they achieve this result without either a significant loss of broad spectrum chemical resistance to harsh geothermal environments or a large increase in cost. Other embodiments also incorporate the use of pozzolanic solids and high alumina cement to further improve chemical resistance characteristics.

FIELD OF THE INVENTION

This invention relates to cementitious compositions. More specifically,the invention is concerned with the compositions of waterless polymerconcretes which can be used as linings for the interiors of pipingsystems handling harsh, high temperature fluids.

BACKGROUND OF THE INVENTION

Many piping system applications in chemical and natural resourcerecovery industries involve the handling of corrosive, erosive, scalingor otherwise harsh aqueous fluids. One economic approach to handlingthese difficult fluids is to spin cast a fluid-resistant liner onto theinterior of a low cost, non-fluid resistant pipe. The pipe material,such as low carbon steel, provides structural support for the costlierand/or structurally inadequate liner. One type of fluid-resistant lineris composed of an inorganic cementitious material, such as concretescontaining Portland cement.

Common concrete lining materials are composed of a variety of inorganicnon-metallic fillers and cements, forming a hydraulic slurry when mixedwith water. The hydraulic slurry, which can temporarily flow like aliquid or plastic, is applied to the interior surfaces of the pipe andallowed to cure (slowly hydrate or precipitate) into a rigid pipe liner.Some water based hydratable cements (e.g., Portland cement) and concreteliners made from same are subject to chemical (e.g., corrosion) andmechanical (e.g., erosive) attack by certain harsh aqueous fluids, suchas geothermal brines.

The primary objectives when creating new material components which canbe used to fabricate a protective pipe liner are that the components: 1)produce a slurry which can be applied to the pipe interior; 2) hardeninto a liner which is attached to and moves with the pipe; and 3) resistlong term fluid chemical and mechanical attack. The lined pipe shouldalso be rugged, safe, reliable, environmentally acceptable, and low incost.

Current cements and/or concretes used to line pipe may perform some ofthese objectives well in some applications, but may not be suitable forother applications. For example, a current American Petroleum Institutepractice (API Recommended Practice 10E) recommends a high sulfateresistant hydraulic (water-based) cement for corrosive waterapplications. However, problems with this type of lining material havebeen observed when handling corrosive geothermal brines.

Many concrete additives or admixtures are known to improve the strengthand chemical stability of a water-based cement/concrete lining material.Additives providing such properties include polymers such aspolystyrene. However, the water base cement is still the primary bondingagent of these additive mixtures

A modification of the hydraulic cement/concrete lining process is topre-coat the carbon steel before lining. An example of this technique isfound in U.S. Pat. No. 4,787,936. High strength and adhesive attachmentof the pre-coat is not required, since the pre-coat is encapsulated(e.g., protected from erosion) by the overlaying cementitious materials.However, the lining must still structurally withstand the environmentand a separate pre-coating process step is required.

A further modification is to post-coat and/or impregnate the pre-formedcementitious liner. An example of this approach is found in U.S. Pat.No. 3,861,944. The post-coating need not bond to the steel pipe.However, the post coating and/or liner impregnation requires a separateprocessing step.

The wide range of in-situ properties of geothermal fluids have made themdifficult to handle using these prior methods. The wide range of fluidproperties is further widened during fluid processing making themsometimes more difficult to handle. Temperatures from ambient to inexcess of 300° C., pH's ranging from highly acidic to basic, anddissolved (and precipitated) solid contents ranging to in excess of 20%by weight of the aqueous mixture are known to cause fluid handlingproblems. Even if the recovery of geothermal fluids is not an objective,these difficult-to-handle fluids may have to be handled during therecovery of oil, gas, and minerals or other natural resource recoveryoperations.

More recently, a waterless cement (i.e., containing insufficient waterto hydrate the cement), filler and polymerizable liquid mixture (termedpolymer concrete) has been developed for geothermal and other difficultapplications. The polymer concrete is typically composed of a solid oraggregate mixture component, such as silica sand filler and Portlandcement, and a polymerizable liquid mixture component. The liquid mixturetypically contains one or more monomers and polymerization additives(e.g., catalysts). The liquid mixture may include cross-linking agents,coupling agents, initiators, solvents/heat dissipators, surfactants,accelerators, and viscosity control compounds.

Because of its cost and desirable properties, some polymer concretecompositions have included styrene as a component. Polystyrene isrelatively water resistant, tends to maintain its shape, and ischemically resistant to many harsh aqueous fluids, such as inorganicliquid acids or bases. However, polystyrene may lack at elevatedtemperature sufficient chemical resistance, strength, and/or toughness,unless co-polymerized and/or cross-linked with other reactiveunsaturates. The styrene molecule has only one reactive hydrocarbon(vinyl) site, thus making the polystyrene chain once formed (i.e., theone site reacted) difficult to cross-link and/or bond strongly toaggregate particles.

In past polymer concrete compositions (as shown in U.S. Pat. No.4,500,674), styrene is combined with at least two different co-monomersto achieve the desired chemical resistance and strength characteristics,one of which is either acrylamide or acrylonitrile. However, thesereactive materials may be toxic and/or carcinogenic. They may alsocompromise low cost fabrication methods (e.g., high temperature mixingand/or curing may be required), broad chemical resistance, andtemperature stability of the resulting liner.

In a modified approach (as shown in U.S. Pat. No. 4,231,917), anothermonomer forms the major polymerizable constituent instead of styrene,but styrene may be a minor constituent. The small amount of styrene isonly one of many possible minority co-monomers. The minority styrenecomposition may further compromise the broad chemical resistance andtemperature performance of a liner when compared to the styrene majoritycomposition.

A persistent problem with these current polymer concrete compositions isthe necessity of trading-off broad spectrum chemical resistance toobtain strength. In addition, none having a majority monomer of styreneavoids requiring two reactive unsaturates/co-monomers, one specified aseither acrylamide or acrylonitrile. Either material adds cost,complexity and health/safety risks to the manufacturing process of afinished product.

Other problems with current polymer concrete compositions are apropensity to crack, the carcinogenic nature of acrylonitrile andacrylamide, and difficulties in solubilizing in styrene and polymerizingacrylamide. Geothermal applications can impose severe conditions such asthermal expansion, thermal shock, vibration, and two phase flowconditions. These conditions tend to crack brittle polymer concreteliners Acrylamide is a solid at ambient temperatures, which requireshigh temperature to mix and co-polymerize with styrene, which is aliquid at ambient conditions. Controlling high temperature during spincasting may be particularly difficult to achieve.

SUMMARY OF THE INVENTION

The present invention minimizes such problems by providing a barrier orlining which is the reaction product of cement, styrene, one or moreco-polymers, and, as an option, a polymer dissolved in the styrene,wherein the styrene/co-polymer/dissolved polymer portion (i.e., liquidcomponent) is composed of at least 50 percent by weight of styrene anddissolved polymer. The composition is essentially free of watersufficient to hydrate the cement, as well as previously requiredacrylamide and acrylonitrile co-monomers. The co-monomers of the liquidcomponent are selected from a group of poly-olefinically unsaturatedcompounds (excluding acrylonitrile or acrylamide). The compositionavoids the need for high temperature curing and other costs associatedwith the excluded compounds.

The materials described in the present invention produce acceptableliner strength under harsh geothermal operating conditions, achievingthis result without a significant loss of broad spectrum chemicalresistance or increase in cost. The liners made from these materialshave been tolerant of off-design conditions, reliable, safe, and costeffective. The materials are also expected to meet the needs of otherdifficult applications. Various embodiments also include the use ofaggregate gradation control, pozzolanic aggregate materials, highalumina cements, and rheology control additives to still further improveprocessing, handling, chemical resistance, and overall cost effectiveperformance of lined pipe.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a process flow schematic for hand trowelled lined pipeapplications; and

FIG. 2 shows a process flow schematic for centrifugally cast lined pipeapplications.

DETAILED DESCRIPTION OF THE INVENTION

The present invention concerns a generally two phase material mixtureused to form a polymer concrete fluid barrier. The two phase compositionincludes a solid particulate (or aggregate) component and a liquidcomponent. The composition is particularly useful to form a polymerconcrete lining bonded to a substrate (i.e., a carbon steel pipe). Inthe preferred embodiment, the two components are mixed, transferred tothe pipe interior and centrifugally spun to shape the liner. Thespinning may also be temporarily halted to drain excess liquid. Theshaped liner can be cured at ambient or elevated temperatures to form ahardened liner. The resulting lined pipe appears to be resistant to arange of contained geothermal fluids, based upon initial testing. Theresulting liners are also expected to be applicable to otherdifficult-to-handle fluid applications, such as process aqueous wastestreams, acid gas handling, boiler blowdown, brine processing, and saltwater heating/ cooling piping.

SOLID OR AGGREGATE COMPONENT

The first of the two components is an aggregate mixture of solidparticles forming at least 5 percent by weight of the material.Compositions having a wide range of aggregate mixtures produceacceptable results. The aggregate mixture typically includes aninorganic cement (e.g., Portland cement) and an inorganic filler (e.g.,particles of a silicious material). An alternative embodiment of thematerial can contain an aggregate mixture composed only of inorganiccement.

An important ingredient of the aggregate component is a dry cement(i.e., a material which forms a slurry or paste when mixed with waterand hardens into a solid or acts as a binding material). Cements aretypically inorganic solids which hydrate or form precipitates afterexposure to water which can react with the cement (i.e., free water).The dry cement may be a partially hydrated mixture, that is, the cementmay have reacted with less water than that required stoichiometricallyto fully react with the cement and binder, requiring additional freewater to form a competent solid or binding matrix. However, it issignificant in the present invention that the cement not be exposed toamounts of free water which would fully harden it into a solid/bindingmaterial during fabrication of the present lined pipe.

The preferred dry inorganic cement is Portland cement. Portland cementcontains CaO as one of the primary oxide constituents. Other significantoxide constituents include CaO, SiO₂ and Al₂ O₃, with other inorganiccompounds and/or metal oxides, such as Fe, Mg, K, S, Na, Ti, and Mnoxide being optionally present in smaller quantities. A compositionalrange reported in weight percent of the chief oxide constituents ofPortland cement is as follows: Calcium Oxide (CaO) 60-67, Silica (SiO₂)17-25, Alumina (Al₂ O₃) 3-8, Iron Oxide (Fe₂ O₃) 0.5-6, Magnesia (MgO)0.1-4, Sulphur Trioxide (SO₃) 1-3, and Soda and/or Potash (Na₂ O+K₂ O)0.5-1.3. The dry powder form of these cements has particles having crosssectional dimensions generally less than 100 microns, typicallyaveraging less than 50-75 microns.

Since the liquid mixture or component to be described hereinaftertypically contains less than 2.0 percent free water by weight of theliquid component and essentially no free water is present in the solidcomponent, the function of the cement is not clear, but is required toobtain the desired properties of the liner. No significant hydration ofthe cement particles appears to occur during the initial hardening phaseof the liner (i.e., polymerization of the liquid component forms thebinder). Even small amounts of water may be detrimental (e.g., a waterfilm formed on the surface of the filler may prevent proper couplingbetween the polymer and the aggregates). Dry cement can help reduce thefree water content (i.e., act as a desiccant or drying agent to removeany water film) which may be present during the curing of the polymer.

Still further, after the lined pipe is placed in service and the linerexposed to harsh aqueous fluids, some or all of the inorganic cementparticles may slowly hydrate. A newly formed hydrate matrix may slowlyoverlay or replace the matrix provided by the polymer. Initial serviceliner properties may therefore not be indicative of later serviceproperties when a geothermal fluid is contained.

The cement may also act as a neutralizer or buffering agent. As an acidor a low pH aqueous fluid permeates the polymer concrete liner, thecement particles may neutralize or raise the pH of the permeatingfluids. The neutralized fluid contacting the substrate carbon steelwould be less likely to be corrosive. In an alternative embodiment,additional quantities of lime (calcium oxide)/hydrated lime are added tothe aggregate to increase this possible neutralizing property of thecement containing composition.

Although how the cement may function in these polymer concretes andgeothermal environments has been discussed, it is not clear. The exactchemical mechanism(s) of cement interactions appear to be highlycomplex. However, the resulting cement interaction properties of thepolymerized liner composed of these cement particles are desirable andsupport the use of the liner in many harsh environments.

Although a liner can be formed using only cement (i.e., containing 100percent cement and no filler), liner properties are more desirable ifboth a non-cement filler and cement are the constituents of theaggregate mix. Only a trace amount of cement in the aggregate componentis required to obtain beneficial results (e.g., removal of a water film)in the fabricated liner properties. The quantity of cement needed is afunction of the filler type and overall composition, processingparameters and application. When the two components (i.e., liquid andsolid components) are mixed and the resultant material centrifugallyspun to form a pipe liner, the optimum ratio of cement to inorganicfiller is controlled to a large extent by the spinning parameters.Generally, the amount of Portland cement used for these conditionsranges from between 10 and 50 percent by weight of the total aggregatecomponent and the maximum amount of Portland cement for more unusualconditions ranges between 5 and 80 percent by weight of the totalaggregate component. Material containing 20 to 30 percent by weight ofPortland cement in the aggregate component has been used tocentrifugally cast pipe liners having superior properties and is thepreferred embodiment.

In an alternative embodiment, a more chemical resistant cement (acidand/or base resistant) has been used. The resistant cement, such as acalcium-aluminate (i.e., high alumina) cement, is used in place ofPortland cement. The Al₂ O₃ and TiO₂ content (i.e., at least 35 percentby weight of the cement) of high alumina cements typically exceeds thatfound in Portland cements. Although high alumina cement has been used toform hydraulic concretes which are more resistant to attack by carbondioxide (a component of many geothermal fluids), other undesirableproperties have made these hydraulic cements less satisfactory forgeothermal service. Again, although the role played by dry, highaluminum cement in polymer concrete is poorly defined, test results showsuperior geothermal service properties for polymer concrete compositionswhich include a high alumina cement. The minimum and maximum amounts ofhigh alumina cement used in the composition are essentially equal to theamounts previously disclosed for Portland cement.

In another alternative embodiment, an expanding cement or non-shrinkingcement (i.e., a cement which does not shrink upon setting after mixingwith water) has been used. An example of non-shrinking cement is amagnesium oxide cement, such as Plastic Porcelain No. 30, supplied bySauereisen Cements Co., Pittsburgh, Pa. Non-shrinking cements may alsobe mixed with other shrinking cements to form an acceptable liner.Again, the role played by these cements in polymer concrete is poorlydefined.

Other types of essentially dry and/or unreacted cements which arenormally reacted with sufficient amounts of water (i.e., free water) toform a bonding matrix (but which are set without substantial amounts ofwater in the composition of this invention) are also acceptable. Thisincludes other silicate based cements and cements which include organicmaterials, such as plastic containing cement. Combinations of differentcements are also possible.

Carefully controlling and limiting the free water content of thematerial during the material handling and forming may be critical tooptimizing polymer concrete liner properties, based upon a series ofrelative strength tests. A styrene, TMPTMA, and catalyst liquid mixturecomponent (as hereinafter described) and a Portland cement and fillersolid component mixture with and without added portions of water wereformed into samples, cured and subjected to strength testing. For thesetests, water was first added to the solid component and allowed to stand1 hour. The polymerizable liquid mixture was then added, mixed andallowed to cure, first at ambient temperature, then at 93° C. (200° F.)for 66 hours.

Testing indicated that water contents of up to approximately 2 percentby weight of the total mixture had little or no effect upon strength(i.e., up to 2 percent added water samples retained at least 90 percentof the strength of samples having no free water). Larger proportions(i.e. greater than 2 percent by weight of the total mixture) of waterproduced significant reductions in strength. The material strength ofsamples having water in excess of 10-12 percent by weight could not bedetermined (i.e., sample crumbled). Based upon these tests, drying,partially dehydrating solids or otherwise driving off free water fromcertain wet materials (e.g., materials which have been exposed toexcessive moisture) prior to mixing and forming the liner may benecessary to obtain optimum liner strength and other properties.

A maximum amount of free water in the aggregate and liquid is the amountrequired to fully react with (e.g., hydrate and be absorbed by) thecement and filler, hereinafter defined as a fully hydrating quantity. Agenerally applicable maximum amount of free water in the aggregate whenno free water has been added to the liquid component is 90 percent ofthe fully hydrating quantity. For more reliable applications, free waterin the aggregate is limited to a maximum quantity of 50 percent of thefully hydrating quantity. For still further reliable applications, amaximum quantity of free water is 10 percent of the fully hydratingquantity. In the preferred embodiment, no free water is added to theaggregate and solid materials exposed to excessive water aredried/dehydrated.

A non-cementitious filler is used as the major remaining constituent ofthe aggregate mixture in the preferred embodiment. The typicallyinorganic (i.e., silicious) filler can be composed of sand, crushedquartz or granite particles. The particles can be in a range of sizes,including powder-like materials, such as silica flour. Although nofiller is required, a filler (i.e., sand including a silica flour)preferably makes up between 30 to 80 percent by weight of the aggregatemixture. In some applications, filler can make up to 90 percent byweight of the aggregate mixture.

In another alternative embodiment, pozzolanic materials/particles areused in the aggregate mixture. The pozzolanic materials include fuel ash(i.e., residue after organic materials have been oxidized), processedoil shale (i.e., residue after organic materials have been removed toproduce a liquid fuel), and geothermal sludges/brine precipitates. Thesepozzolanic particles may be acid washed prior to use in the polymerconcrete.

Although pozzolanic materials have been used in hydraulic cements, thefunction of the pozzolanic materials in waterless polymer concrete hasnot been fully determined. Pozzolanic materials are known to stabilizePortland cement when hydrated. In the polymer concrete of thisinvention, the pozzolanic materials may slowly combine with the freelime during any water uptake and inorganic cement hydration. Sincehydroxides, such as calcium hydroxide, are reactive (i.e., readilysubject to chemical attack by geothermal fluids), this combination witha pozzolanic material may improve the chemical resistance of thehydrated cement which might form.

Particle sizes of the aggregate (cement and other filler particles)mixture are gradated in the preferred embodiment to form a smooth top orinner surface. The filler can include a powder-like silica flour,defined herein as a silicious material having an average particlecross-sectional dimension of less than 100 microns, typically in therange of 5 to 30 microns. The proportion of silica flour as a weightpercent of the aggregate component is essentially unlimited, buttypically ranges from 5 to 30 percent.

Using gradated filler (i.e., a distribution of filler particle sizes)reduces fluid requirements and minimizes the tendency to form an overlythick skin or surface layer. An undesirable overly thick skin iscomposed of an excessive amount of cement sized particles and polymer asa result of the spin/centrifugal casting process. The aggregatematerials, having different sizes and densities, tend to segregateduring agitation or centrifuging. The lighter and more easily suspendedparticles and liquids tend to concentrate at the top (or at the insidediameter of centrifuged liners), forming a smooth desirable surface.Poorly gradated filler can result in overly thick, crack-prone skins orinadequate substrates by depleting the quantity of fine filler materialin the main body of the liner. Use of specific gradated aggregates canresult in a desirable surface (i.e., smooth skin surface) while limitingexcessive segregation tendencies.

A representative distribution (reported in terms of weight percentageand size gradation of the cement and silicious particles) is given inTable 1 as follows:

                  TABLE 1                                                         ______________________________________                                        GRADATION OF AGGREGATE PARTICLE SIZES                                         Sieve Size Range, mm.                                                                           Weight Percent                                              ______________________________________                                        Filler, 1.400-1.180                                                                             1.0                                                         Filler, 1.179-0.850                                                                             6.0                                                         Filler, 0.849-0.425                                                                             14.0                                                        Filler, 0.424-0.250                                                                             28.0                                                        Filler, 0.249-0.180                                                                             3.0                                                         Filler, 0.179-0.106                                                                             7.0                                                         Filler, 0.105-0.002                                                                             17.0                                                        Cement, <0.05     24.0                                                        ______________________________________                                    

It is beneficial to have at least a two peak (i.e., bi-modal)distribution of particle sizes (i.e., a frequency distribution ofparticle sizes peaking at two or more size ranges). One of the peaks inthe particle size distribution is that belonging to a powder-likematerial or flour. The second, sometimes overlapping peak, is thatbelonging to particle sizes representative of cement. Another peakdenotes particles whose diameter is greater than that of the flourmaterial by at least one order of magnitude.

Control of the maximum size particle as well as the distribution ofsizes (i.e. gradation) is important in obtaining optimum results,especially for spun or centrifugally cast liners. The maximum particlesize is a function of liner thickness and consequently the pipediameter, as well as other factors. The maximum particle size isgenerally less than about 2.4 mm for common pipe and for liner sizescurrently used in geothermal applications, preferably less than 1.4 mm.

Controlling the ratio of the quantity of the silica flour portion of theaggregate to the quantity of the cement portion of the aggregate is amethod of directly controlling cured liner properties and indirectlyinfluencing slurry viscosity and skin thickness. A nominal ratio of fourparts cement to one part silica flour has produced a lining havingdesirable properties and is the preferred embodiment; however a range ofcement:flour ratios from 2:1 (two parts cement to one part silica flour)to 8:1 (eight parts cement to one part silica) and higher also producesliners having acceptable properties. The more general range ofcement:silica flour ratios is from 5:2 to 4:1. A maximum silica flourcontent of 30 percent by weight of total solids is a typical practicallimit independent of the cement:silica flour ratio.

An alternative embodiment especially useful for hand trowellingapplications includes fibrous and/or fibrous shaped fillers in themixture. The fibers are generally composed of inorganic materials, suchas glass, but may also be composed of other materials, such as graphite.Although fibers of almost any length and diameter can be used, fiberlengths rarely exceed 0.6 cm (0.25 inch) for practical handlingconsiderations. Average fiber diameters typically range from 10 to 20microns (0.0004 to 0.0008 inch) in diameter. Average fiber lengthstypically range from 0.3 to 0.4 cm (0.12 to 0.16 inch) and the mostcommon aspect ratio (i.e., length to diameter) ranges from approximately100 to 200.

For the purposes of this invention, it is intended that the term "fiber"or "fibrous filler" encompass materials which may have polar functionalgroups in the form of relatively short filaments as well as longerfibers often referred to as "filaments." Illustrative polar functionalgroups contained in suitable fibers are hydroxyl, ethereal, carbonyl,carboxyl, thiocarboxyl, carboxylate, thiocarboxylate, amido, amino, etc.Essentially all natural fibers include one or more polar functionalgroups. Illustrative are virgin and reclaimed cellulosic fibers such ascotton, wood fiber, coconut fiber, jute, hemp, etc., and protenaceousmaterials such as wool and other animal fur. Illustrative syntheticfibers containing polar functional groups are polyesters, polyamides,carboxylated styrene-butadiene polymers, etc. Illustrative polyamidesinclude nylon-6, nylon 66, nylon 610, etc.; illustrative polyestersinclude "Dacron," "Fortrel," and "Kodel"; illustrative acrylic fibersinclude "Acrilan," "Orlon," and "Creslan." Illustrative modacrylicfibers include "Verel" and "Dynel." Illustrative of other useful fiberswhich are also polar are synthetic carbon (i.e., graphite), silicon,boron and magnesium silicate (e.g., asbestos) polymer fibers andmetallic fibers such as aluminum, gold, and iron fibers. The use ofnon-polar fibers are also possible in alternative embodiments.

In another alternative embodiment, a small amount (additive) of a solidconstituent is added to the solid and liquid mixture to obtain a desiredrheology (i.e., slurry or mortar mix/paste consistency). Cab-O-Sil andHi-Sil have been found to be effective as a thickening or rheologycontrol additives for hand trowelling applications whereby the resultingthixotropic material is manually applied to the pipe interior. The twospecific additive materials are currently supplied by Cabot (Cab-O-Sil)and PPG (Hi-Sil) companies. Such additives are believed to be composed,at least in part, of amorphous silica and appear to be highly surfacereactive. These amorphous silica additives soak up the "liquidcomponent" after mixing, adding tackiness and body to the two componentmixture while not significantly affecting the kinetics ofpolymerization.

These viscosity additives are not required but can be used infabricating centrifugally cast liners. Additives were found to be verybeneficial in hand lining, repair, and patching operations. The slurrymixtures containing these additives are highly thixotropic and easy toapply, and remain in place until hardening has taken place.

The range of amorphous silica additives (Cab-O-Sil M-5 or EH-5, andHi-Sil T-600) that can be added to form as much as 25 percent or more byweight, but for practical (i.e., cost, etc.) purposes is restricted to amaximum of 6.0 percent by weight of the solid component (i.e., aggregatemix) comprising the material. Lower concentrations (at least 0.5percent, typically at least 1.5 percent, but less than 3.0 percent byweight of the aggregate component) are normally sufficient to enhancethe thixotropic properties of the mix.

Although other constituents may be present in the solid or aggregatemixture, specifically limited or excluded is acrylamide. Significantquantities of acrylamide were previously cited (i.e., in U.S. Pat. No.4,500,674) as important to the integrity of a polystyrene majoritypolymer cement. Testing of material made from aggregate and specificliquid constituents hereinafter described, but excluding acrylamideand/or acrylonitrile, has yielded positive results. Liners produced frommixtures which contain no detectable amounts of acrylamide and/oracrylonitrile have been found to withstand harsh geothermalenvironments. However, minor amounts of acrylamide and/or absorbedacrylonitrile, i.e., less than one percent by weight of the solidcomponent, are acceptable.

LIQUID COMPONENT

The liquid component is composed of a combination of styrene, at leastone co-monomer, and an optional dissolved polymer, forming a fluidmixture. The combination of the styrene and any dissolved polymercomposes at least 50 percent of the fluid mixture. The next largestconstituent of the liquid component is an olefinic substance, typicallyat least one polymerizable poly-olefinically unsaturated co-monomer inthe form of a fluid. The styrene, co-monomer(s), and solubilizablepolymer fluid mixture polymerizes to form an aggregate binder or bindingmatrix for the solid component. The binder comprises at least 5 weightpercent of the resulting (non-homogeneous) liner material. Because ofmixing, compaction and drainage during spinning, 10 percent by weight ofthe total is a preferred minimum proportion of liquid component. Theoptimum proportion of liquid is a function of spin rate, spin time andagggregate properties.

The dissolved polymer is typically composed of a homopolymer of styrene,i.e., polystyrene. The polystyrene is pre-dissolved/premixed typicallywith the styrene, but the polystyrene or other polymer may also bepre-dissolved/premixed with the liquid co-monomer(s) or the fluidmixture.

The total styrene plus polystyrene content is generally greater than 50percent by weight of the liquid component. Preferably, thestyrene/polystyrene mixture content varies from 55 to 95% by weight ofthe total liquid component, and more preferably from 60 to 90 percent byweight of the total liquid component.

In an alternative embodiment, styrene can be used without a polymer inthe liquid component; however, a premixed polymer has been found toimprove the properties of some fabricated liners (e.g., lessfracturing). The polystyrene, when used, appears to act as a thickeningagent and as a plasticizer after polymerization. The maximum amount of adissolved polymer is limited only by styrene solubility considerations,but 14 weight percent dissolved polystyrene in styrene appears to be apractical sytrene mixture limit. Choosing the optimal proportion ofpolystyrene is dependent upon factors such as liner fabricationtemperature and spinning parameters, with typical proportions rangingfrom 5 to 10 weight percent.

The amount of styrene mixture in the liquid component is a function ofthe specific polymerizable reactive unsaturate (i.e., co-monomer)chosen. The specific co-monomer(s) used are selected from a specificgroup of poly-olefinically unsaturated compounds. The molecularstructure of these compounds is characterized by at least two reactiveolefinic bonds, and typically containing at least onehydrocarbon-containing vinyl group. The preferred monomer has 4 to about40 carbon atoms and at least 2 vinyl substituents per molecule. Themonomer molecule may contain carbonyl, carboxyl, hydroxyl, thiol,thiocarbonyl, carboxylic acid ester, thioester, amine, amide, silane,silanol, siloxane, and combinations thereof. The carbon containingcompounds may also contain heteroatoms, such as one or more membersselected from the group consisting of nitrogen (N), oxygen (O), andsulfur (S).

The poly-olefinically unsaturate can also be characterized as compoundsfrom one or more of the following groups: hydrocarbonolefins havingabout 4 up to about 20 atoms; olefinically unsaturated vinyl esters,thioesters; amides of saturated carboxylic acids having up to about 20carbon atoms; esters, thioesters, and amides of olefinically unsaturatedcarboxylic acids having up to about 20 carbon atoms; polyesters,thioesters, and amides of saturated polyhydric alcohols; thiols,polyamides, and olefinically unsaturated carboxylic acids having up toabout 20 carbon atoms; polyesters, thioesters and amides of saturatedpoly-carboxylic acids and olefinically unsaturated alcohols, thiols, andamides; and polyhydrocarbenyl silanes and siloxanes having up to about20 carbon atoms per molecule.

The initial tests have shown that several compounds within thispoly-olefinic unsaturate/vinyl compound group produce acceptable linersfor geothermal environments. These include:trimethylolpropane-trimethacrylate; divinyl benzene; hexadiene;polyvinylmethylsiloxane; andgamma-methacryloxypropyl-trimethyloxysilane. In view of the foregoing,it is clear that one can employ related compounds as co-monomers. Theserelated compounds include: vinyl containing compounds, such as vinylbenzenes; dienes, preferably having a molecular structure characterizedby from 5 to 15 carbon atoms; and a group of silicone substitutedmolecules containing at least two reactive vinyl groups, such aspolyvinylsiloxanes and polyvinyl silanes.

Specifically limited or excluded from the composition of the liquidcomponent are significant amounts of dissolved acrylamide andacrylonitrile co-monomers. Both of these materials are costly and canalso be considered known or potential carcinogens. Since acrylamide is asolid at ambient temperature, an elevated temperature and extensivemixing are also required to polymerize compositions which contain it.Extensive heated mixing and transfer of the amount needed to line a 40foot pipe section create still further costs and problems. Thecomposition (liquid and solid components) excludes or limits these twospecific co-monomers (acrylamide and/or acrylonitrile) and theirderivatives to less than a significant amount (defined quantitativelyherein as less than 3 percent by weight of the total composition).Preferably, very small amounts (defined herein as less than 1 percent byweight of either the liquid or the solid component) of either one orboth of these co-monomer compounds may be tolerated, but compositionswhich exclude acrylamide and acrylonitrile are most preferred forsafety, cost and handling ease.

Also specifically limited or excluded from the liquid component of thecomposition is free water (i.e., water that is available to react withthe aggregate mixture). An absolute maximum quantity of free water inboth the aggregate mixture is the amount required to fully react withthe aggregate mixture (i.e., the fully hydrating quantity). A moregenerally applicable maximum amount of free water in the liquidcomponent when dry aggregate is used is 90 weight percent of the fullyhydrating quantity. For more general applications, the free water in theliquid component is limited to 50 weight percent of the fully hydratingquantity. A more reliable maximum value of free water is to limit it tono more than 10 weight percent of the fully hydrating quantity. In thepreferred embodiment, no free water is added to the liquid mixture,except for a small amount associated with the catalyst.

The proportion of one or more co-monomers as a weight percent of theliquid component varies depending upon the specific co-monomer(s) used.Overall, the co-monomer proportion can range from 0.5 percent to nearly50 percent by weight of the liquid component, preferable less than 45percent by weight. The maximum practical amounts of some of the specificco-monomers which have produced acceptable liner properties expressed asa weight percentage of the total liquid component are as follows: 40percent trimethylolpropane-trimethacrylate; 25 percent divinyl benzene;15 percent of polyvinylmethylsiloxane; 15 percent hexadiene; and 10percent gamma-methacryloxypropyl-trimethyloxysilane. The minimumpractical amount of each of these specific co-monomers is 0.5 percent byweight of the liquid component; usually at least a proportion of aboutfive percent by weight of the liquid component.

In small amounts (e.g., less than about 7 liquid weight percent in someinstances), one or more of the co-monomers, such asgamma-methacryloxypropyl-trimethyloxysilane, is thought to actexclusively as a coupling agent. This coupling agent co-monomer appearsto be chemically absorbed by or to coat the inorganic particles andprovides reactive vinyl attachment sites for the bulk polymer phase,increasing material strength. Increasing the proportion ofgamma-methacryloxypropyl-trimethyloxysilane over 7 percent has littlefurther effect on material strength. That is, it appears to have fullycoated the solids, with the excess acting as an additional co-monomer inthe bulk polymer phase. The coupling agent may also fully encapsulatethe inorganic particles, when used in higher concentrations.

A relatively small portion of the remaining liquid component istypically composed of polymerization additive(s) or catalyst(s), definedas materials which control the onset and/or rate of polymerization(e.g., initiation or acceleration additives) of the styrene andco-monomer(s). Although a polymerization additive is not required, atrace amount (i.e., minimum detectable amount) is beneficial to controlpolymerization. The maximum amount of each of these additives is limitedprimarily by practical limits, such as set times, material performance,and cost.

Solutions of the useful monomers and polymers can be prepared byprocedures known in the art to be suitable for the preparation of thestyrene and poly-olefinically unsaturated monomers reacting to form apolymer solid or binder. For instance, monomers, solvents and/or polymerdispersions can be prepared by gradually adding each monomersimultaneously to a reaction medium at rates proportionate to therespective percentage of each monomer in the finished polymer andinitiating and continuing polymerization by providing in the reactionmedium a suitable polymerization catalyst. Illustrative of suchcatalysts are free radical initiators and redox systems such as hydrogenperoxide, potassium or ammonium peroxydisulfate, dibenzoyl peroxide,lauryl peroxide, di-tertiary-butyl peroxide, bisazodiisobutyronitrile,either alone or together with one or more reducing components such assodium bisulfite, sodium metabisulfite, glucose ascorbic acid,erythorbic acid, etc. The reaction can also be controlled with agitationand temperature sufficient to maintain the reaction rate until allmonomers are consumed.

Six percent by weight of the liquid is a maximum practical proportionallimit of each polymerization additive or catalyst. The proportion ofeach polymerization additive is typically limited to a range of from0.25 to 3.0 percent by weight of the liquid component, and moretypically limited to a range of from 0.5 to 1.5 percent by weight.

A specific initiator found particularly useful is benzoyl peroxide. Thishas been shown to be effective in initiating rapid polymerization atambient conditions. A nominal 1.0 percent solution (by weight of theliquid monomeric component) of benzoyl peroxide has been used in some ofthe testing. Methylethylketone peroxide has also been found to be analternative and/or higher temperature initiator or catalyst.N,n,-dimethylaniline and cobalt napthenate have been particularly usefulas accelerators (each also at a nominal concentration of 1% by weight ofthe liquid component).

Alternative embodiments do not include an initiator or accelerator.Although polymerization can be accomplished without catalysts andcontrolled by thermal or other means in this alternative embodiment, thepreferred method (using catalysts) allows ambient temperature curing andfield handling of the composition.

FIG. 1 shows a process by which the two component mixture describedabove can be used for hand trowelling applications. The mixing step "A"of the trowelling application blends all the liquid components with theinitiators and accelerators at ambient temperature conditions prior tomixing with the aggregate component. In an alternative process, theaggregate is first mixed with a liquid coupling agent which coats and/orencapsulates the solid particles. The coating provides a reactivesurface which can polymerize internally or with monomers constitutingthe bulk of the liquid phase. In the alternative process, the remainderof the liquid components are then mixed with the aggregate instead ofmixing all the liquid components prior to combining with the filler asshown in FIG. 1.

In the next process step "B," the solid component is mixed at ambienttemperature with the liquid mixture to form a mortar or thick concreteslurry. This must be accomplished well before gelation of the liquid mixhas occurred (as characterized by a gel time). A typical example of agel time when using catalysts is 25-45 minutes. Mixing the initiator(s)and accelerator(s) into the monomeric liquid (Step "A") begins thegelation process, and the remaining slurry process steps (steps "C" and"D") must be accomplished within this gel time. For hand trowellingapplications, a rheology control additive is typically included in thesolid aggregate mixture, as previously discussed.

In the next process step "C," the thickened slurry is transferred andapplied to the interior of the piping section. This slurry applicationis typically by hand transfer, but can also be sprayed, pumped, drained,ladled or otherwise transferred.

In the next process step "D," the material is formed into the desiredshape. This can be accomplished by hand forming (e.g., trowelling) or byusing casting forms. Liners can be patched or gaps between linersections filled using similar techniques.

In the final process step "E," the liner is allowed to cure at ambienttemperature. Hardening progresses as the polymerization proceeds. In analternative embodiment, another processing step is added wherein thematerial is post cured at elevated temperature(s), either at dryconditions and/or when exposed to a hot aqueous fluid, such as ageothermal brine. High temperature curing at 71° C. (160° F.) or higheris usually necessary for siloxane cross-linked systems.

FIG. 2 shows a process of using the two component mixture as describedabove for centrifugal casting applications. The first step "AA" is tomix the solid and liquid components, except for the initiator(s) andaccelerator(s) to form a slurry. Two initiators (benzoyl peroxide andmethylethylketone peroxide) were generally used, one reactive at a lowtemperature and one designed to be reactive at higher temperatures.Mixing step "AA" can be accomplished by first pre-mixing the solids(i.e., commingling and breaking up agglomerates) and then adding andmixing the liquid component (without the initiator and/or accelerator)to obtain a desired slurry consistency. An alternative to the first step"AA" is to mix solids, liquids and initiators, but withhold theaccelerator (or visa versa). The slurry thus formed (without either theaccelerator or initiator) can generally be flowed for extended periodsof time.

The next step "BB" is to add the polymerization initiator(s) and/oraccelerator(s) to the mixture. The addition(s) are mixed into theslurry. The addition(s) begin the gelation process and defines theworking period within which the liner must be cast. This adding step"BB" is followed by a transfer step "CC" wherein the slurry is conveyedand applied to the pipe interior. Conveyance may be accomplished bymeans such as pumping the liquid-like slurry, gravity flow of the slurryvia troughs, belt, auger or portable trough conveyance.

The pipe and transferred slurry are then spun around the pipe'scylindrical axis to shape the material into a liner in spinning step"DD". The centrifugal force during the spin casting distributes theslurry material on the interior pipe surface. Dams or barriers areplaced at the ends of the pipe sections to retain the material in placeprior to and during centrifuging.

In the final hardening step "EE," the liner is allowed to cure. The curenormally occurs at ambient temperature for a time sufficient to hardenit for service in geothermal or other applications. Elevated temperature(i.e., oven) post curing may be employed, and is preferred for somemixtures, especially when polyvinylsiloxane is the reactive unsaturate.Exposing the liner to aqueous fluids at elevated temperatures (e.g.,geothermal fluids), may also be provided to further harden the liner aspart of a post curing step.

When excess polymerizable liquids are present during curing and/orspinning, alternative process step(s) can be provided. These added stepssplit the spinning step, wherein the excess fluids are allowed to drainfrom the section after an initial spinning step. The section can then bere-spun to minimize slumping, etc. In the initial spinning step, theliner is shaped and the aggregate compacted sufficiently t allow thedrainage of excess fluids. In the re-spinning step, the liner is allowedto harden to the extent that further drainage or slumping is precluded.

Unless a release compound or separation material is placed at thespinning mixture's liner/pipe interface, the hardened and cured linercomponent is bonded (i.e., adheres) to the pipe after the castingprocess. In an alternative embodiment, release compound may be appliedto the steel piping or fitting (now serving as a form) to create aseparate concrete pipe/fitting having an outer diameter equal to theinside diameter of the pipe/fitting form. In modified embodiments,partial bonding of the liner to the pipe or pipe sections, connectors orfittings may allow some relative motion (e.g., resulting from thermalexpansion) of the liner with respect to the pipe/fitting. Thepipe/fitting can also be pre-treated with a coupling agent or mechanicalbonding system (e.g., a welded screen) to facilitate bonding to theliner.

Still other alternative embodiments are possible. These include: aplurality of liner segments within a single pipe section separated byelastomeric or plastic seals; extending the liner beyond the end of thepipe section to interconnect with tanks or other equipment; having theouter pipe composed of other materials, such as other structural metals,relatively rigid elastomers, plastics, concrete, porous or insulatingmaterials. Other alternatives are to place an intermediate materialbetween the pipe wall and liner (i.e., pre-coat the pipe interior), oradd a protective enclosure or external covering to the steel pipe.

The invention satisfies the need to provide a low cost, easy to applyliner to steel pipe for use in harsh geothermal or other environments.The dry cement, other aggregate, and the monomers are relativelynon-toxic. Costly acrylamide and acrylonitrile have been limited orexcluded from the mixture. The mixture hardens to provide a strongthermally stable liner without compromising chemical stability.

Further advantages of the invention include: increased safety,(eliminates need for carcinogenic materials), reliability (as little asa single co-monomer plus coupling agent, if required, reducescomplexity), and lower cost (no high temperature cure and major use ofan inexpensive styrene).

EXAMPLES

The invention is further described by the following examples which areillustrative of specific modes of practicing the invention and are notintended as limiting the scope of the invention in any manner as definedby the appended claims. The examples are polymer samples (bottle tests)and liners which were fabricated during the initial testing phase:

EXAMPLE 1

A series of liquid mixtures using the co-monomertrimethylolpropane-trimethacrylate (TMPTMA) and catalyst(methylethylketone peroxide and di-t-butyl peroxide were prepared in ajar or bottle. Initial curing occurred at a temperature of about 38° C.(100° F.) for a period of approximately 4-5 hours each. Initialinspection results from one series are shown in Tables 2-4 as follows:

                  TABLE 2                                                         ______________________________________                                        LIQUID MIXTURES 1, INITIAL BOTTLE TEST RESULTS-                               EXAMPLE 1                                                                     ______________________________________                                        Constituent weight %                                                          styrene  97     93     89   85   94   90   86   82                            polystyrene                                                                            0      4      8    12   0    4    8    12                            TMPTMA   2      2      2    2    5    5    5    5                             MEKP/    1      1      1    1    1    1    1    1                             DTBP                                                                          Results                                                                       liquid/gel/                                                                            g      g      g    g    g    g    g    g                             fuse                                                                          React.   0      0      0    0    0    0    0    0                             strength                                                                      Cracking 0      0      0    0    0    0    0    0                             Crazing  0      0      0    0    0    0    0    0                             Color    o      o      o    o    o    o    o    o                             Clear    c      c      c    c    c    t    c    c                             Layers   1      1      1    1    1    1    1    1                             ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        LIQUID MIXTURES 2, INITIAL BOTTLE TEST RESULTS-                               EXAMPLE 1                                                                     ______________________________________                                        Constituent weight %                                                          styrene  90     86     82   78   75   71   77   73                            polystyrene                                                                            0      4      8    12   0    4    8    12                            TMPTMA   10     10     10   10   25   25   25   25                            MEKP and 1      1      1    1    1    1    1    1                             DTBP                                                                          Results                                                                       liquid/gel/                                                                            g      g      f/g  f/g  g    f/g  f/g  f/g                           fuse                                                                          React.   0      0      0    0    0    0    0    0                             strength                                                                      Cracking 0      0      0    0    0    0    0    0                             Crazing  0      0      0    0    0    0    0    0                             Color    o      o      w/o  w/o  w/o  w/o  w/o  w/o                           Clear    c      t      t    t    c    t    t    t                             Layers   1      1      1    1    1    2    2    2                             ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        LIQUID MIXTURES 3, INITIAL BOTTLE TEST RESULTS-                               EXAMPLE 1                                                                     ______________________________________                                        Constituent weight %                                                          styrene  59     55     51   47   40   36   32   28                            polystyrene                                                                            0      4      8    12   0    4    8    12                            TMPTMA   40     40     40   40   59   59   59   59                            MEKP and 1      1      1    1    1    1    1    1                             DTBP                                                                          Results                                                                       liquid/gel/                                                                            g      f/g    f/g  f/g  g    f    f    f/g                           fuse                                                                          React.   0      0      0    0    0    0    0    0                             strength                                                                      Cracking 0      0      0    0    0    0    0    0                             Crazing  0      0      0    0    5    2    1    0                             Color    o      w/o    w/o  w/o  b    w    w/o  w/o                           Clear    c      --     --   --   --   --   --   --                            Layers   1      2      2    2    1    1    2    2                             ______________________________________                                         Nomenclature for tables 2-4 is as follows:                                    liquid/gel/fuse: 1 = liquid; g = gel; and f = fuse                            React. Strength: arbitrary 0-5 scale, force to remove                         Cracking: arbitrary 0-5 scale, 0 = no cracking                                Crazing: arbitrary 0-5 scale, 0 = no crazing                                  Color: w = white, y = yellow, o = olive, b = blue, a = amber                  Clear: c = clear, t = turbid, p = opaque                                      Layers: number of layers observed                                        

The inspections shown above in Tables 2-4 were accomplished at about 27°C. (80° F.) over a 7 hour period. After these inspections, the bottlesample were then cured at 93° C. (200° F.) for a period of approximately19 hours, and the inspections repeated. Inspections were accomplished atroom temperature conditions. Final inspection results are shown inTables 5-7 as follows:

                  TABLE 5                                                         ______________________________________                                        LIQUID MIXTURES 1, FINAL BOTTLE TEST RESULTS-                                 EXAMPLE 1                                                                     ______________________________________                                        Constituent weight %                                                          styrene  97     93     89   85   94   90   86   82                            polystyrene                                                                            0      4      8    12   0    4    8    12                            TMPTMA   2      2      2    2    5    5    5    5                             MEKP and 1      1      1    1    1    1    1    1                             DTBP                                                                          Results                                                                       liquid/gel/                                                                            g      g      g/f  g/f  g    g/f  g/f  g/f                           fuse                                                                          React.   --     --     --   --   --   --   --   --                            strength                                                                      Cracking 0      0      0    0    1    1    0    0                             Crazing  5      5      3    3    0    0    0    1                             Color    b      b      w/b  w/b  p    p/w  b/w  b/w                           Clear    c      c      t/c  t/c  c    t/c  c/t  c/t                           Layers   1      1      2    2    1    2    2    2                             ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        LIQUID MIXTURES 2, FINAL BOTTLE TEST RESULTS-                                 EXAMPLE 1                                                                     ______________________________________                                        Constituent weight %                                                          styrene  90     86     82   78   75   71   77   73                            polystyrene                                                                            0      4      8    12   0    4    8    12                            TMPTMA   10     10     10   10   25   25   25   25                            MEKP and 1      1      1    1    1    1    1    1                             DTBP                                                                          Results                                                                       liquid/gel/                                                                            g      g/f    f    f    g    f    f/g  f                             fuse                                                                          React.   --     1      --   --   --   --   --   --                            strength                                                                      Cracking 0      1      0    0    0    0    0    0                             Crazing  0      1      0    0    0    0    0    0                             Color    b      p/w    w    w    y    w/y  p/w  p/w                           Clear    c      c/t    t    t    c    t/c  c/t  c/t                           Layers   1      2      1    1    1    2    2    2                             ______________________________________                                    

                  TABLE 7                                                         ______________________________________                                        LIQUID MIXTURES 3, FINAL BOTTLE TEST RESULTS-                                 EXAMPLE 1                                                                     ______________________________________                                        Constituent weight %                                                          styrene  59     55     51   47   40   36   32   28                            polystyrene                                                                            0      4      8    12   0    4    8    12                            TMPTMA   40     40     40   40   59   59   59   59                            MEKP and 1      1      1    1    1    1    1    1                             DTBP                                                                          Results                                                                       liquid/gel/                                                                            g      f      f/g  f/g  g    f    f    f/g                           fuse                                                                          React.   --     --     --   --        1    --   --                            strength                                                                      Cracking 0      0      0    0    0    1    2    0                             Crazing  5      0      0    0    5    2    0    0                             Color    b      w/y    y/w  y/w  b    w    w    w/b                           Clear    c      t/c    c/t  c/t  c    t    t    t/c                           Layers   1      2      2    2    1    1    1    2                             ______________________________________                                         Nomenclature for Tables 5-7 is the same as tables 2-4.                   

Based upon these bottle results and other bottle test results withcompositions having other co-monomers catalysts, and curing parameters,liner compositions were selected.

EXAMPLE 2

Based upon the aforementioned bottle tests, aggregate mixtures (i.e.,solid component) and a liquid mixtures (i.e., monomer/dissolved polymercomponent) were prepared and mixed to form a slurry. The solid (Table 8)and liquid (Table 9) component compositions are as follows:

                  TABLE 8                                                         ______________________________________                                        AGGREGATE MIXTURE-EXAMPLE 2                                                   Constituent          Aggregate weight %                                       ______________________________________                                        Gradated silica sand, excluding flour                                                              66.3                                                     Silica flour (less than 0.075 mm                                                                   9.7                                                      average dimensional size)                                                     Portland Cement, Class G                                                                           24.0                                                     ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        LIQUID MIXTURE-EXAMPLE 2                                                      Constituent           Liquid weight %                                         ______________________________________                                        Styrene               49.0                                                    Polystyrene           8.0                                                     Trimethylolpropane-trimethacrylate                                                                  37.0                                                    Gamma-methacryloxypropyl-                                                                           3.5                                                     trimethyloxysilane (A-174)                                                    Benzoyl peroxide (BPO)                                                                              1.0                                                     Dimethyl aniline (DMA)                                                                              1.0                                                     Methylethylketone peroxide (MEKP)                                                                   0.5                                                     ______________________________________                                    

The gradation of silica sand was similar to that shown in Table 1. Theamount of liquid component in the mixture varied from between 11.5 and16 percent of the total weight of the slurry for centrifugally castliner specimens. The liquid constituents listed in Table 9 were addedtogether (including BPO, DMA & MEKP) and mixed prior to adding (pouringonto) to the aggregates designated in Table 8, along with othercompositions. The average ambient temperature was roughly 27° C. (80°F.). Using a slurry delivery system primarily based upon gravity flow,the mixture was transferred to the interior of one or more pipesections. Each pipe section was fitted with slurry containment devices(e.g., fluid dams) at each end. The pipe sections were then spun aroundthe pipe centerline axis. The centrifugal force generated distributedthe slurry out against the interior pipe wall, thus forming the fluidbarrier which fully lined the interior of the steel pipe. The excessfluid was drained off and the material allowed to gel. Gelation occurredapproximately 40 minutes following the mixing of the accelerator in withaggregate slurry.

The test liners fabricated were roughly 1.3-2.5 cm (0.5-1.0 inch) thickand bonded to the interior of pipe sections having nominal diameters ofless than 61 cm (24 inches). Fabrication was generally accomplishedduring summertime ambient conditions.

Sections, including those having the tabulated compositions, were thenselected for testing. Some of the sections were oven cured at elevatedtemperatures; others were allowed to cure at ambient temperature until atest location was made available. The pipe sections were then installedand tested as a part of several geothermal brine pipelines. Brinetemperatures of up to 240 degrees Celsius were recorded.

After exposure to the brine for at least several months, the initialtest specimens were inspected. Little or no corrosion of the pipe wallwas evident, and the lining material was found to be mechanically soundbased primarily upon visual inspection. No major failure or significantloss of material was noted.

EXAMPLE 3

An aggregate mixture and a liquid mixture were prepared as per Tables 10and 11 to fabricate lined pipe test specimens. The process was similarto that described in Example 2. Compositions were as follows:

                  TABLE 10                                                        ______________________________________                                        AGGREGATE MIXTURE-EXAMPLE 3                                                   Constituent        Aggregate weight %                                         ______________________________________                                        Gradated silica sand and flour                                                                   70                                                         Processed oil shale                                                                              6                                                          Portland cement, type III                                                                        24                                                         ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                        LIQUID MIXTURE-EXAMPLE 3                                                      Constituent        Liquid weight %                                            ______________________________________                                        Styrene               49.4                                                    Polystyrene           8.0                                                     Trimethylolpropane-trimethacrylate                                                                  38.2                                                    Gamma-methacryloxypropyl-                                                                           2.4                                                     trimethyloxysilane                                                            Methylethylketone peroxide (MEKP)                                                                   1.0                                                     Cobalt naphthenate - 6% (CON)                                                                       0.5                                                     Di-t-butyl peroxide (DTBP)                                                                          0.5                                                     ______________________________________                                    

Results prior to exposure to brine were comparable to Example 2 results.No major failures were evident.

EXAMPLE 4

Aggregate and liquid mixtures were prepared as per Tables 12 and 13 tofabricate lined pipe test specimens. The process was similar to Example2, except the ambient temperature during casting was approximately 100degree Fahrenheit. Compositions were as follows:

                  TABLE 12                                                        ______________________________________                                        AGGREGATE MIXTURE-EXAMPLE 4                                                   Constituent          Aggregate weight %                                       ______________________________________                                        Gradated silica sand (including flour)                                                             76                                                       Calcium aluminate cement                                                                           24                                                       (>40 percent Al.sub.2 O.sub.3)                                                ______________________________________                                    

                  TABLE 13                                                        ______________________________________                                        LIQUID MIXTURE-EXAMPLE 4                                                      Constituent           Liquid weight %                                         ______________________________________                                        Styrene               81.1                                                    Polystyrene           7.1                                                     Trimethylolpropane-trimethacrylate                                                                  9.8                                                     Methylethylketone peroxide (MEKP)                                                                   1.0                                                     Cobalt naphthenate - 6% (CON)                                                                       0.5                                                     Di-t-butyl peroxide (DTBP)                                                                          0.5                                                     ______________________________________                                    

Results prior to brine exposure were comparable to Example 2 results. Nomajor failures were evident.

EXAMPLE 5

An aggregate mixture and a liquid mixture component were prepared as perTables 14 and 15 to fabricate liquid pipe test specimens. The processwas similar to that described in Example 4. Compositions were asfollows:

                  TABLE 14                                                        ______________________________________                                        LIQUID MIXTURE-EXAMPLE 5                                                      Constituent           Liquid weight %                                         ______________________________________                                        Styrene               53.9                                                    Polystyrene           7.4                                                     Divinyl benzene       24.5                                                    Hexadiene             9.8                                                     Gamma-methacryloxypropyl-                                                                           2.4                                                     trimethyloxysilane                                                            Methylethylketone peroxide (MEKP)                                                                   1.0                                                     Cobalt naphthenate - 6% (CON)                                                                       0.5                                                     Di-t-butyl peroxide (DTBP)                                                                          0.5                                                     ______________________________________                                    

                  TABLE 15                                                        ______________________________________                                        SOLID AGGREGATE MIXTURE-EXAMPLE 5                                             Constituent          Aggregate weight %                                       ______________________________________                                        Gradated silica sand (including flour)                                                             76                                                       Portland cement, Type III                                                                          24                                                       ______________________________________                                    

Results prior to brine exposure were comparable to Example 2 results. Nomajor failures were evident.

EXAMPLE 6

An aggregate mixture and a liquid mixture were prepared as per Tables 16and 17 to fabricate lined pipe test specimens. The process was similarto that described in Example 2. The samples were thermally cured atapproximately 71° or 93° C. (160° or 200° F.) for a period of 24 hourseach. Compositions were as follows:

                  TABLE 16                                                        ______________________________________                                        AGGREGATE MIXTURE-EXAMPLE 6                                                   Constituent          Aggregate weight %                                       ______________________________________                                        Gradated silica sand (including flour)                                                             76                                                       Portland cement, Type III                                                                          24                                                       ______________________________________                                    

                  TABLE 17                                                        ______________________________________                                        LIQUID MIXTURE-EXAMPLE 6                                                      Constituent        Liquid weight                                              ______________________________________                                        Styrene            75.9                                                       Polystyrene        10.3                                                       Polyvinylmethylsiloxane                                                                          9.9                                                        Gamma-methacryloxypropyl-                                                                        2.4                                                        trimethyloxysilane                                                            Benzoyl peroxide (BPO)                                                                           1.0                                                        Di-t-butyl peroxide (DTBP)                                                                       0.5                                                        ______________________________________                                    

Results prior to brine exposure were comparable to Example 2 results. Nomajor failures were evident.

In all of the previous examples, no water was added. The solidcomponent, if present, was observed to be dry, although some uptake ofmoisture may have occurred. In addition, at least one of the catalysts(i.e., polymerization additives) is known to be supplied as a wateremulsion for safety and handling reasons.

While the preferred embodiment of the invention has been shown anddescribed, and some alternative embodiments and examples also shownand/or described, changes and modifications may be made thereto withoutdeparting from the invention. Accordingly, it is intended to embracewithin the invention all such changes, modifications and alternativeembodiments as fall within the spirit and scope of the appended claims.

What is claimed is:
 1. A composition for forming a solid material, thecomposition characterized as a two component mixture which comprises:anaggregate component comprising a cement which reacts with water to forma solid binder material; and a polymerizable liquid component comprisingstyrene and at least one olefinically unsaturated monomer polymerizablewith styrene and being free of acrylamide and acrylonitrile, whereinsaid styrene constitutes a major weight portion of said polymerizableliquid component, and an amount of reacted and/or free water less thanthe amount of water required to hydrate said cement.
 2. The compositionof claim 1 wherein the styrene includes a dissolved portion ofpolystyrene and wherein the amount of free water is less than about 2percent by weight of the liquid component.